The respiratory variation in inferior vena cava diameter as a guide to fluid therapy.

OBJECTIVE: To investigate whether the respiratory variation in inferior vena cava diameter (DeltaD(IVC)) could be related to fluid responsiveness in mechanically ventilated patients.

DESIGN: Prospective clinical study.

SETTING: Medical ICU of a non-university hospital.

PATIENTS: Mechanically ventilated patients with septic shock (n=39).

INTERVENTIONS: Volume loading with 8 mL/kg of 6% hydroxyethylstarch over 20 min.

MEASUREMENTS AND RESULTS: Cardiac output and DeltaD(IVC) were assessed by echography before and immediately after the standardized volume load. Volume loading induced an increase in cardiac output from 5.7+/-2.0 to 6.4+/-1.9 L/min (P<0.001) and a decrease in DeltaD(IVC) from 13.8+/-13.6 vs 5.2+/-5.8% (P<0.001). Sixteen patients responded to volume loading by an increase in cardiac output > or =15% (responders). Before volume loading, the DeltaD(IVC) was greater in responders than in non-responders (25+/-15 vs 6+/-4%, P<0.001), closely correlated with the increase in cardiac output (r=0.82, P<0.001), and a 12% DeltaD(IVC) cut-off value allowed identification of responders with positive and negative predictive values of 93% and 92%, respectively.

CONCLUSION: Analysis of DeltaD(IVC) is a simple and non-invasive method to detect fluid responsiveness in mechanically ventilated patients with septic shock.